Rotary cutter for machining materials

ABSTRACT

Novel endmills are provided. Such endmills have a body with outside diameter (OD), and outer surface, and a longitudinal axis, a plurality of flutes, helical in some embodiments. Flutes include a narrow leading edge land portion with circular segment profile and having flute cutting edge portions along a substantially uniform circumferential location, with an eccentric relief margin rotationally rearward of the narrow leading edge land portions. Face portions are provided with face cutting edge portions, and with a first dish portion adjacent each of the cutting edge portions sloping inwardly and downwardly generally toward a central longitudinal axis at a first dish angle alpha (α). Corner blend portions extend from flute cutting edge portions to the face cutting edge portions. Corner blend portions are provided in a variety of profiles, including an embodiment wherein the profile of the corner blend portions are truncated before the segment of curvature becomes tangential to the face cutting edge portions. In various embodiments, one or more coolant passageways are provided, and in an embodiment, an exit port for coolant is provided at the center of rotation of the end face portion.

STATEMENT OF GOVERNMENT INTEREST

Not Applicable.

COPYRIGHT RIGHTS IN THE DRAWING

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The patent owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

RELATED PATENT APPLICATIONS

This application is a continuation of prior and now pending U.S. patentapplication Ser. No. 16/444,948 filed Jun. 18, 2019, which applicationclaims priority under 35 USC § 120 and was a continuation of prior U.S.patent application Ser. No. 14/964,183 filed Dec. 9, 2015, (now U.S.Pat. No. 10,335,870 issued Jul. 2, 2019), which application claimedpriority under 35 USC § 120 and was a continuation of U.S. applicationSer. No. 12/750,701 filed on Mar. 30, 2010, (now U.S. Pat. No. 9,227,253B1, issued Jan. 5, 2016), which application claimed priority from priorU.S. Provisional Patent Application Ser. No. 61/164,902, filed Mar. 30,2009, entitled ROTARY CUTTER WITH MULTIPLE CUTTING EDGES. Thedisclosures of each of the just noted prior related patent applicationsis incorporated herein in their entirety, including the specification,drawing, and claims, by this reference.

TECHNICAL FIELD

The present invention relates to rotary tools, and more specifically, toend mill cutting tools for use in multi-axis cutting machine operations.

BACKGROUND

In the machine tool industry, those of skill in the art will recognizethat end mills are generally provided as cylindrically shaped cuttingtools with a shank end and a cutting end having flutes (with or withouthelix design) that define side cutting edges which intersect with theend of the end mill, generally with a slight concave dish of from about1 to about 3 degrees of inward dish angle (that is, from the radialedges inward toward the center of rotation). The existing end millcutting tools of which we are aware are provided based on designs thatare generally capable of plunging or pecking with multiple small axialsteps, or which are capable of ramping at relatively slight angles, suchas between about one-half (½) degree to about three (3) degrees. Theactual degree of ramping achievable is often primarily dependent uponthe machineability of the material being cut. In many such machine tooldesigns, exceeding such just mentioned ramping angles during machiningon a workpiece causes elevated cutting forces, and possibly catastrophicfailure, due to excessive tool to part contact. Such failures are, inpart, due to inefficient geometry of cutting face design of such priorart tools.

To avoid such problems, various techniques have been developed, and suchprior art techniques are presently widely used in machining workpieces.For example, the technique of pocketing may be utilized, wherein onefirst uses a drill to manufacture a hole, and then the end mill isinserted into the hole, and subsequently a slot is machined in a lateraldirection. Another method, namely slotting, may be utilized, where anopen end allows machining to start at an outside or exposed edge, andmultiple slot cuts of shallow depth are utilized. The first approach,i.e. pocketing, requires the use of two tools—a drill and an end mill.Both techniques require multiple machining steps. Thus, both of thosetechniques are inefficient. Extra time is consumed during partsmanufacture by the use of such processing techniques. And, in manyrespects, high or excessive cutting pressure may decrease tool life.Also, the cutting pressure or heat generated in such prior arttechniques may decrease the quality of the part made from the workpiecebeing machined.

One relatively recent patent, namely U.S. Pat. No. 6,435,780, issuedAug. 20, 2002 to C. M. Flynn for a Rotary Cutting Tool has made anattempt at reducing forces encountered during end milling. However, onlymaterial listed in the published test results was 6061-T85 aluminum,which material is very easy to machine. Thus, such test results do notshow that such designs are qualified to avoid problems which areinevitably encountered when ramp machining the many and various harderor higher tensile strength materials. In the tool disclosed in thatpatent, an end mill having a shank end and a cutting end having flutesdefining side cutting edges is provided. However, a periphery end edgeportion is defined that slopes at an angle which in various embodimentsmay be somewhere in the range of about two (2) degrees or slightly more,and an interior edge portion is defined that slopes at an angle in therange of five (5) to twenty five (25) degrees. Thus, while such an endmill design may help to reduce the forces while ramping, such design isfaced with the problem of chipping or plastic deformation of theworkpiece at the working face, e.g., the outer most corner of rotationof the tool. Further, it does not provide geometry for dampening orreducing the effects of model coupling (the effect of which would betool chatter). When ramping at angles greater than about three (3) tofive (5) degrees, the result in simultaneous multi-axis machining withsuch a tool is that the combined directional movements form a singlechip at two adjacent shear zones. These zones are located around eightysix (86) degrees from each other at the outer most tip of the cuttingedges of the radial diameter, where it meets the end cutting edgeforming a sharp point or tip. In the case of that tool, the chip formedis in the same shear zone at the dish end of the end mill and theoutside periphery, both intersecting at the tip or corner. When thosetwo opposing faces form a simultaneous chip at the same shear zone orchip path, they collide and compress as their directional pathsintersect each other. The effect of creating two chips simultaneously inthe same shear zone is more than doubling in both heat and cuttingpressure at such point of intersection. When such phenomenon occurs,chips are forced and buckled as neither the shear zone near the tip orat the tip itself has a clear path for chip flow. This leads toadditional strain and increased forces as the chip is then cold formedin the gullet of the flutes, resulting in additional tool pressure andheat. At this point of intersection both the heat and cutting pressureor strain is increased at the weakest point of the tool, i.e., thecorner of the tool. Also, such prior art tool design does not control orallow for sufficient room for chip flow. With no specific geometry foraccommodating chip formation or chip removal paths, during use, such atool would lead to higher tool pressure at such shear zones, leading tochipping of the corner of the workpiece, or wear of the workpiece due toplastic deformation from the resulting strain and heat.

Consequently, there still remains an as yet unmet need for an end milltool design, and a method for operation of milling machines when usingsuch end mill tools, that takes full advantage of improved mechanicaldesign components with respect to cutting angles and cutting speed ofthe improved rotary cutters disclosed and claimed herein.

Moreover, it would be advantageous to accomplish such goals whileproviding a rotary cutting tool suitable for use in existing millingequipment, and while providing a procedure for modification of existingparts manufacturing programs, in order to increase productivity ofmanufacturing operations of machined parts, and especially, thosemachined parts that would benefit from high speed rough end millingoperations.

SUMMARY

A high speed rotary cutting tool that is especially useful for highspeed rough end milling operations is described herein. Such high speedrotary cutting tools, and in particular, end milling tools, providesignificantly improved performance in the art of simultaneous multi axismachining. Importantly, the high speed rotary cutting tool, and inparticular, end milling tools taught herein, allow machining operationsat increased surface speeds, with higher workpiece feed rates, yet whileproviding increased rotary cutting tool life.

As a result of advances in machine tools (e.g., computer numeric controlor “CNC” machine tools), and computer aided machining software (“CAM”software), cutter paths can be provided in terms of constant toolengagement angle. Rotary cutting tools can be controlled by algorithmsin software to provide a consistent chip in terms of chip length and achip thickness. Such constant tool engagement angles are generallyprovided in terms of not to exceed ramp angle or engagement speed,regardless of a varying cutter path. This technique in turn producesrelatively uniform chips that are roughly equal in length given aconsistent thickness and duration of cut. Such machining techniquesprovide relatively consistent cutting forces in terms of loads, heatgenerated, and time exposed to heat, thereby limiting the forces andtemperatures allowed to be reached. Such machinery and software thusallows for the use of rotary cutters, provided such cutters have thecutting geometry that can facilitate running at much higher surface feetper minute rates. Such improved rotary cutters can employ aggressiveramp angles, circular interpolated plunging, or helical interpolation,as cutter paths for entry into the workpiece material. By providing anovel rotary cutter design as described herein, the capability ofpresently available machine tools and their software can be exploited,and thus provide significantly improved productivity and capability in amilling cutter. Further, novel rotary cutting tool designs enablemulti-axis directional feeds, and machining surface speeds thatheretofore have been impossible to reliably and consistently obtain inthe use of multidirectional rotary cutters, especially rotary end millcutters.

An improved rotary cutter is provided in a configuration especiallysuited for, but not limited in use to, rough end milling of workpieces,such as metallic parts. The rotary cutter has a body with a shankportion having a lower end, and a cutting portion. The cutting portionhas flutes extending upward along said body from a lower or proximalflute end. In an embodiment, helical flutes may be provided. The fluteshave a leading edge land portion that is provided as a narrow landwidth, which in an embodiment is of the same diameter as the shank ofthe cutter, and at the leading edge thereof a flute cutting edge isprovided. Rearward of the flute cutting edge and the narrow width land,rotationally, is at least one margin relief portion, which in anembodiment may be an eccentric relief margin. The rotary cutter has aface portion having a plurality of face cutting edge portions. Variousembodiments may be provided with the number of face cutting edgeportions ranging, for example, in the range of two (2) to seven (7)flutes for cutters in the range of from about one-eighth (⅛) inch orless to about one and one-half (1.5) inches or so. The face cutting edgeportions are provided at the rotationally forward edge of a downwardlyand inwardly sloping first dish portion. Corner blend portions areprovided which extend from the flute cutting edge to corresponding facecutting edge portions. In an embodiment, the corner blend portions havean outer surface curvature defined by a segment of curvature shaped froma conic element, and wherein said segment of curvature is truncatedbefore becoming tangential to said cutting edge portion. In variousembodiments, the segment of curvature may be truncated at from betweenabout four (4) degrees and about seventy (70) degrees before the segmentof curvature becomes tangential to the face cutting edge portion. In anembodiment, the corner blend portions may be provided by a chamferconfiguration. In various embodiments, the first dish portion isprovided sloping inwardly at an angle in the range of from about fivepoint five (5.5) degrees to about twenty five (25) degrees. For example,in an embodiment, a rotating cutter having three flutes may be providedwith a first dish portion that is sloping downwardly and inwardly at anangle of about twelve point five (12.5) degrees. For example, in anembodiment, a rotating cutter having five flutes may be provided with afirst dish portion that is sloping downwardly and inwardly at an angleof about eight point five (8.5) degrees. And, in a further embodiment, arotating cutter having seven flutes may be provided with a first dishportion that is sloping downwardly and inwardly at an angle of about six(6) degrees. Further, in various embodiments, a second dish portion isprovided that downwardly and inwardly slopes at an angle in the range offrom about twenty five (25) to about seventy (70) degrees. In variousembodiments, coolant passageways are provided to support lubrication andcooling between the rotary tool and the workpiece, and to supportremoval of chips.

In an embodiment, such new high speed rotary cutting tools may enablethe operator of milling equipment to substantially increase thethroughput of parts in current milling equipment, by substantiallyincreasing the speed of milling, commonly measured, in one aspect, assurface feet per minute (“SFM”) that a cutting tool moves through aworkpiece, i.e., the surface speeds maintained during cutting, or inanother aspect as machine removal rate (“MRR”), i.e, the amount ofmaterial removed from a workpiece per unit of time. In an embodiment,such high speed rotary cutting tools are capable of creating relativelyuniform chips from workpieces while working at high surface speeds on aworkpiece. In yet another embodiment, such high speed rotary cuttingtools are capable of providing cooling and lubrication while operatingat high surface feed per minute through a workpiece, thus furtherenhancing their utility and increasing productivity in milling machineryutilizing such new rotary cutting tools.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will be described by way of exemplary embodiments,using for illustration the accompanying drawing in which like referencenumerals denote like elements, and in which:

FIG. 1 is a side elevation view of an embodiment of a rotary cuttingtool, wherein the cutting tool comprises five flutes and uses amechanical flat or indexing slot for locating the shank portion of thetool in a milling machine.

FIG. 2 is a side elevation view of an embodiment of a rotary cuttingtool, similar to the view just shown in FIG. 1, but now showing ashorter tool without an indexing slot for securing the shank portion ina milling machine.

FIG. 3 provides a face end view of a rotary cutting tool justillustrated in FIG. 2 above, now showing the face portion of the cuttingtool with five face cutting edge portions, and a downwardly and inwardlysloping first dish portion adjacent each face cutting edge portion, afurther downwardly and inwardly sloping second dish portion inwardlyadjacent the first dish portion, as well as corner blend portionsextending from each flute cutting edge portion to each face cutting edgeportion.

FIG. 4 provides a side elevation view of an embodiment of a rotarycutting tool, similar to that first shown in FIG. 1 above, now showing acutting tool with five flutes, and which also utilizes a coolantpassageway, here shown provided along a longitudinal axis at therotational centerline.

FIG. 4A provides a side elevation view of a rotary cutting tool, similarto that first shown in FIG. 4 above, now showing a cutting tool withfive flutes, and which also utilizes a single entry port for a coolantpassageway, but using multiple coolant passageways to feed coolant tovarious flutes.

FIG. 4B provides a side elevation view of another embodiment of a rotarycutting tool, similar to that first shown in FIG. 4A above, but nowshowing a cutting tool which also utilizes multiple coolant passagewayentry ports and multiple coolant passageways to exit ports along aplurality of flutes.

FIG. 5 is a detailed close up side view of the working end of the rotarycutter just shown in FIG. 4, now showing in detail the flutes and a thinleading edge land portion having a flute cutting edge, and an eccentricmargin relief portion, and parts of the face portion, and the downwardlyand inwardly sloping first dish portion adjacent each face cutting edgeportion, and corner blend portions extending from flute cutting edge tothe face cutting edge portions.

FIG. 6 is a face view of the rotary cutter just shown in FIG. 5 nowshowing in detail the parts of the face portion including the downwardlyand inwardly sloping first dish portion adjacent each face cutting edgeportion, the downwardly and inwardly sloping second dish portion, andcorner blend portions extending from flute cutting edge to the facecutting edge portions.

FIG. 7 shows another embodiment of a rotary cutting tool, [[ere]] nowshowing the use of three flutes with flute cutting edge portions andthree face cutting edge portions, as well as the use of a mechanicalflat or indexing slot for locating the shank portion of the tool in amilling machine.

FIG. 8 shows yet another embodiment of a rotary cutting tool, similar tothe tool just shown in FIG. 7, but here further showing the use ofsmoothly radiused coolant/chip passageways along the flutes.

FIG. 9 is a detailed close up side view of the working end of the rotarycutter just shown in FIG. 7, now showing in detail the flutes and a thinleading edge land portion having a flute cutting edge, and an eccentricmargin relief portion, and parts of the face portion, including thedownwardly and inwardly sloping first dish portion adjacent each facecutting edge portion, and corner blend portions extending from flutecutting edge to the face cutting edge portions.

FIG. 10 is a face view of a rotary cutter similar to that just shown inFIG. 9, now showing in detail the parts of the face portion includingthe downwardly and inwardly sloping first dish portion adjacent eachface cutting edge portion, and corner blend portions extending fromflute cutting edge to the face cutting edge portions.

FIG. 11 is a face view of a rotary cutter similar to that just shown inFIGS. 9 and 10, but here more precisely showing in detail parts of anexemplary face portion including the downwardly and inwardly slopingfirst dish portion adjacent each face cutting edge portion, a downwardlyand inwardly sloping second dish portion, and corner blend portionsextending from flute cutting edge to the face cutting edge portions.

FIG. 12 is a side elevation view of the rotary cutter similar to thatjust shown above in FIG. 8, but now showing the use of a longer flutecutting edge having a plurality of v-shaped notched coolant/chippassageways along the flutes.

FIG. 13 is a close-up view a portion of a flute of the embodiment justillustrated in FIG. 12 above, now showing in detail a narrow leadingedge land portion having a circular grind, thus providing an arcuateland shape, and having a honed flute cutting edge at the forward orrotary edge of the leading edge land portion, as well as showing aneccentric margin relief portion.

FIG. 14 is a side elevation view of yet another embodiment of a rotarycutting tool, wherein the cutting tool utilizes two flutes, and showingin detail the downwardly and inwardly sloping first dish portionadjacent each face cutting edge portion, a further downwardly andinwardly sloping second dish portion inwardly adjacent the first dishportion, as well as corner blend portions extending from flute cuttingedges to face cutting edges.

FIG. 15 provides a face end view of a rotary cutting tool justillustrated in FIG. 14 above, now showing the face portion of thecutting tool with two face cutting edge portions, and showing in detailthe downwardly and inwardly sloping first dish portion adjacent eachface cutting edge portion, a further downwardly and inwardly slopingsecond dish portion inwardly adjacent the first dish portion, as well ascorner blend portions extending from each flute cutting edge portion toeach face cutting edge portion.

FIG. 16 provides a detailed partial side view of a portion of the rotarycutting tool just illustrated in FIGS. 14 and 15 above, showing indetail the downwardly and inwardly sloping first dish portion adjacenteach face cutting edge portion, as well as corner blend portionsextending from each flute cutting edge portion to each face cutting edgeportion, and the face of the gullet of the flute which extendsrearwardly from the face cutting edge of the positively raked flute.

FIG. 17 provides a partial side view of a portion of yet anotherembodiment for a rotary cutting tool, wherein only a single or firstdish portion is utilized, rather than a first and second dish portion asshown in various other embodiments, however, the downwardly and inwardlysloping first dish portion adjacent each face cutting edge portion isshown, as well as corner blend portions extending from each flutecutting edges to face cutting edges.

FIG. 18A provides a perspective view of a portion of a rotary cutter,showing one embodiment for a corner blend portion, wherein anon-tangential intersection is provided with the first dished portion.

FIG. 18B shows a perspective view of a portion of a rotary cutter,showing an embodiment with a corner blend portion where a tangential ornear tangential intersection is provided with the first dished portion.

FIG. 18C provides a perspective view of yet another embodiment for arotary cutter, illustrating the use of one or more chamfers to provide asuitable corner blend portion.

FIG. 19 provides a diagrammatic view of a rotary cutter, illustratingsome optional features for spacing of helical flutes.

FIG. 20 provides a diagrammatic view of a workpiece being milled inaccord using the novel rotary cutter set forth herein.

FIG. 21 provides a schematic view of a rotary cutter in use to machine aworkpiece, and describes key cutting concepts, including tool feed pertooth, tool engagement angle, radial depth of cut, and chip thickness.

FIG. 22 provides a cross-sectional view of a rotary cutting tool,similar to the tool first illustrated in FIG. 15 above, now illustratinga two (2) flute endmill having a core diameter of at least sixty percent(60%) of the tool diameter.

FIG. 23 provides a cross-sectional view of a rotary cutting tool,similar to the tool first illustrated in FIG. 10 above, now illustratinga three (3) flute endmill having a core diameter of at least sixtypercent (60%) of the tool diameter.

FIG. 24 provides a cross-sectional view of a rotary cutting tool,illustrating a four (4) flute endmill having a core diameter of at leastsixty percent (60%) of the tool diameter, and more particularly in thisillustration, having a core diameter of slightly more than sixty eightpercent (68%) of the tool diameter.

FIG. 25 provides a cross-sectional view of a rotary cutting tool,illustrating a five (5) flute endmill having a core diameter of at leastsixty one percent (61%) of the tool diameter, and more particularly inthis illustration, having a core diameter of at least sixty four percent(64%) of the tool diameter.

FIG. 26 provides a cross-sectional view of a rotary cutting tool,illustrating a six (6) flute endmill having a core diameter of at leastsixty three percent (63%) of the tool diameter, and more particularly inthis illustration, having a core diameter of at least sixty five percent(65%) of the tool diameter.

FIG. 27 provides a cross-sectional view of a rotary cutting tool,illustrating a seven (7) flute endmill having a core diameter of atleast sixty four percent (64%) of the tool diameter.

FIG. 28 shows a cross-sectional view of a rotary cutting tool,illustrating a seven (7) flute endmill having a core diameter of atleast sixty four percent (64%), and more particularly in thisillustration, having a core diameter of at least sixty eight percent(68%) of the tool diameter.

The foregoing figures, being merely exemplary, contain various elementsthat may be present or omitted from actual rotary cutting tool designsfor endmills or other tools as taught herein, or in methods that may beimplemented for use of such tools. Other rotary tool designs may useslightly different mechanical configurations, but be mechanicallydesigned with a configuration as is described for utilizing elementsdescribed herein or depicted in the drawings shown herein. An attempthas been made to draw the figures in a way that illustrates at leastthose elements that are significant for an understanding of the varioustool designs and methods taught herein for improving the efficiency ofmilling operations when utilizing tool designs as set forth herein.Further, it should be understood that groupings of similar parts arenoted with similar numbers having different subscript or other relatedindicia, and some parts specifically mentioned in the specification arenot explicitly noted where not visible in the provided drawing figures,it being considered unnecessary to provide still further drawings toexplain to those of skill in the art the structure of repeated yetseparately noted components so noted and numbered. However, it should beunderstood that various features may be utilized in accord with theteachings hereof, as may be useful in different embodiments as necessaryor useful for cutting various materials or as may be desirable dependingupon the end uses of such workpieces.

DETAILED DESCRIPTION

An exemplary rotary cutting tool design is set forth herein, as well asa method for use of such tools in milling machines to improvemanufacturing productivity. Attention is directed to FIG. 1, whichillustrates an end mill type milling cutter 100, which has acylindrically shaped body 102 having a longitudinal axis noted bycenterline 104. The body 102 has a shank portion 106 with lower end 108,and a usable cutting portion 110. As further explained hereinbelow (andbriefly noted in FIG. 2) a selected axial depth of cut (ADC) in therange of from about one point five (1.5) times the outside diameter (OD)of a cutter 100 to about three (3) times the outside diameter (OD) of acutter 100 may be advantageously achieved where the usable cuttingportion 110 is of sufficient length A_(L). Shank portion 106 may includea machine mounting feature 112 such as a flat shown in this FIG. 1. Inother embodiments, alternate machine mounting features may includeWeldon flats, a whistle notch, a straight flat, a flat groove, or aradial groove, for securing the shank portion 106 in a tool holder (notshown) in a milling machine (not shown).

The cutting portion 110 may, in an embodiment such as shown in FIG. 1,have a plurality of circumferentially extending ribs such as flutes 114,which flutes are discretely and individually identified by referencenumerals 114 _(A), 114 _(B), 114 _(C), 114 _(D), and 114 _(E). In anembodiment, such as is shown in FIG. 1, the flutes 114 may be providedin a generally spiraling configuration about a cylindrically shaped body102. In an embodiment, the flutes 114 may be provided in a helicalconfiguration spaced around cutting portion 110. In an embodiment, aflute 114 such as the discrete flute 114 _(A) runs from a proximal orlower flute end (for example, see 1168 or 116 _(C)) adjacent thetransition point 118 of the shank portion 106 up to a distal end 120_(A) at the corner blend portion 122 _(A). It will be understood tothose of skill in the art and to whom this specification is directedthat corresponding parts for other flutes will have, in an embodiment,similar features, and thus repetition of companion reference numbers forcorresponding parts is thus unnecessary. Likewise, common parts may beshown in the drawings with differing subscript suffix to differentiatebetween similar elements, without the necessity to repeat the preciseidentification of each similar element using a different subscriptsuffix. As shown, the cutting portion 110 is provided with a pluralityof flutes, which in the embodiment shown in FIG. 1 is five flutes,namely flutes 114 _(A), 114 _(B), 114 _(C), 114 _(D), and 114 _(E).However, different embodiments of a rotary cutting tool may be providedwith one or more flutes, and more typically, with two or more flutes,and even more typically, with three or more flutes. Other embodimentsare shown and described below having four flutes, five flutes, sixflutes, and even seven flutes, all in accord with the teachings hereof.

For purposes of illustration, attention will be directed to a singleflute 114 _(A), however, it should be appreciated that for the presentembodiment, such discussion may be applied generally to the variousflutes on milling cutter 100. The cutting portion 110 of the millingcutter 100 has flutes such as flute 114 _(A) with an undercut portionsuch undercut 130 _(A) that provides a gullet between adjacent flutessuch as between flutes 114 _(A) and 114 _(B). The flute 114 _(A) has aleading edge land portion 132 _(A) that has a flute cutting edge 134_(A). With respect to the orientation of the flute relative to theundercut 130 _(A) and the flute cutting edge 134 _(A), the flute 114_(A) may be provided with a rake angle or orientation that, in anembodiment, may be negative, or neutral, or in the embodiment shown inFIGS. 1, 2, and 3, may be positive. In an embodiment, the flute cuttingedge 134 _(A) may be provided in a generally circumferentialconfiguration, in that the flute cutting edge 134 _(A) may be located atthe periphery (i.e. about the outer diameter “OD”) of the generallycylindrically shaped cutter body 102. The leading edge land portion 132_(A) is provided without relief, and thus for its very narrow lengthrearward from the flute cutting edge 134 _(A), may be provided as ashort arcuate land having the radius R₁₀₂ of the cutter body 102.Rearward of the leading edge land portion 132 _(A) there is provided atleast one margin relief portion 136 _(A), which in an embodiment, may bean eccentric shaped relief margin. Thus, the at least one margin reliefportion 136 _(A), especially when provided in eccentric configuration,provides increasing in clearance rearward from the point of intersectionof a workpiece with leading edge land portion 132 _(A) behind the flutecutting edge 134 _(A). In an embodiment, the flute cutting edge 134 _(A)may be provided as a honed edge. Similarly, in an embodiment, the facecutting edge portions 154 _(A) (discussed below) may be provided as ahoned edge.

Attention is directed to FIGS. 12 and 13, wherein in FIG. 12, a threeflute cutter 137 is provided, and wherein in FIG. 13, the just mentioneddetails of flute cutting edge 134 _(A), and the leading edge landportion 132 _(A) provided without relief are shown in enlarged detail.In FIG. 13, it is easy to see that for its very narrow length rearwardfrom the flute cutting edge 134 _(A), the leading edge land portion 132_(A) is provided without relief, as a short arcuate land having theradius R₁₀₂ of the cutter body 102 (see FIG. 3). Thus, the leading edgeland portions 132 _(A) operate as arcuate lands moving along theperiphery P of cutter rotation, which is at the circumference of thecutter 100C as defined by the outer diameter OD of the body of cutter100C, as noted in the cutting face view of FIG. 6. The leading edge landportions 132 _(A) are provided in a selected length L (see FIG. 13) offrom about 0.0001 inches to about 0.002 inches, rearward of said flutecutting edge 134 _(A), based on said rotary cutter outer diameter (OD,which for example, is two times R₁₀₂ as depicted in FIG. 1), as setforth in the following table:

OD (inches) selected length L (inches) Under ⅛ .00010 to .0005 ⅛ to 3/16.00010 to .0010 3/16 to ¼ .00015 to .0012 ¼ to 5/16 .00020 to .0015 5/16to ⅜ .00025 to .0015 ⅜ to ½ .00030 to .0015 ½ to ⅝  .00035 to .00175 ⅝to ¾ .00040 to .0020 ¾ to 1 .00045 to .0020 1 to 1.5 .00050 to .0020Over 1.5  .00050 to .0020.

Further, the detail of FIG. 13 also shows the use of at least one marginrelief portion 136 _(A), which in an embodiment, may be an eccentricshaped relief margin. As also seen in FIG. 13, a second relief margin138 _(A) is provided. Thus, it may be clearly seen that the at least onemargin relief portion 136 _(A) when provided in eccentric configuration,provides increasing working clearance rearward from the point ofintersection a workpiece with leading edge land portion 132 _(A). Whilethe least one margin relief portion 136 _(A) in the flutes is shown withan elliptical relief margin, which is often the most practicalconfiguration, it should be understood that the least one margin reliefportion 136 _(A) may alternately be provided as a straight relief angledsurface, as well as a curved relief surface, whether radial, elliptical,or other conic configuration.

Attention is now directed to FIGS. 1, 2, and 3, with respect to thecutting end or face portion 150 of cutter 101 depicted in FIG. 3. Afirst dish portion 152 _(A), 152 _(B), 152 _(C), 152 _(D), 152 _(E)(extending from each flute that runs to the upper end 151 of the cutter100, respectively) slopes downwardly and inwardly (along respectivefirst face cutting edge portions 154 _(A), 154 _(B), 154 _(C), 154 _(D),154 _(E)) at a first dish angle alpha (α). In an embodiment, the firstdish angle alpha (α) may be in the range of from about 6 degrees toabout 25 degrees. As shown in FIG. 1, first dish angle alpha (α) isrepresented as between a line H perpendicular to the longitudinal axis104 and slope S₁ of the first dish portions 152 _(A), 152 _(B), 152_(C), 152 _(D), and 152 _(E). Separately, in an embodiment, a selectedrelief margin 155 _(A), 155 _(B), 155 _(C), 155 _(D), 155 _(E)respectively (which may be flat as illustrated or with otherconfiguration as desirable for a particular application) may be providedrotationally rearward of the first face cutting edge portions 154 _(A),154 _(B), 154 _(C), 154 _(D), 154 _(E) respectively.

Also as may be appreciated from FIGS. 1 and 3 together, a second dishportion, 156 _(A), 156 _(B), 156 _(C), 156 _(D), 156 _(E) slopesdownwardly and inwardly (along a respective second face cutting edgeportions 158 _(A), 158 _(B), 158 _(C), 158 _(D), 158 _(E), respectively)at a second dish angle beta (β). In an embodiment the second dish anglebeta (β) may be in the range of from about 25 degrees to about 70degrees. As shown in FIG. 1, second dish angle beta (β) is representedas between a line H perpendicular to the longitudinal axis 104 and slopeS₂ of the second dish portions 156 _(A), 156 _(B), 156 _(C), 156 _(D),and 156 _(E). Separately, in an embodiment, a selected relief margin(which may be flat as illustrated or with other shape (see FIGS. 18A,18B, 18C, and 19) as may be desirable for a particular application) maybe provided rotationally rearward of the second face cutting edgeportions 158 _(A), 158 _(B), 158 _(C), 158 _(D), 158 _(E), respectively.

Further attention is directed to FIGS. 1, 2, and 3 together, where thecorner blend portions (122 _(A), 122 _(B), 122 _(C), 122 _(D), 122 _(E),respectively) are shown extending from their respective flute cuttingedge (134 _(A), 134 _(B), 134 _(C), 134 _(D), 134 _(E), respectively,noting that 134 _(C) and 134 _(D) are not shown but are similar to theirillustrated counterparts) to their companion first face cutting edgeportions (154 _(A), 154 _(B), 154 _(C), 154 _(D), 154 _(E),respectively). The corner blend portions 122 _(A), etc. may be providedin various precise shapes as appropriate for a particular service. In anembodiment, as shown in FIG. 1, the corner blend portions 122 _(A), etc.have an outer surface curvature 159 defined by a segment of curvatureshaped from a conic element. In an embodiment, the conic elementdefining the outer surface of the corner blend portions 122 _(A) etc.may be provided at least in part by an elliptical shaped surfaceelement. In an embodiment, the conic element defining the outer surfaceof the corner blend portions 122 _(A) etc, may be provided at least inpart by segments from a hyperbolic shaped surface element. In anembodiment, the conic element defining the outer surface of the cornerblend portions 122 _(A) etc. may be provided at least in part by acircular shaped surface element having a radius R_(C), as noted in FIG.18A.

As also shown in FIG. 18A, in an embodiment that is useful forcontrolling chip size and to enhance cutting ability of a rotary cutterprovided as described herein, the segment of curvature used to providethe corner blend portions 122 _(A), etc. may be truncated beforebecoming tangential to their respective face cutting edge portion, e.g.,first face cutting edge portion 154 _(A) By one measure, in variouspossible embodiments, the segment of curvature used to provide thecorner blend portions 122 _(A), etc. may be truncated by an angle delta(Δ) of from about four (4) degrees to about seventy (70) degrees beforethe segment of curvature defining the corner blend portion, e.g., 122_(A) becomes tangential to the first face cutting edge portion 154 _(A).In some embodiments, the segment of curvature used to provide the cornerblend portions 122 _(A), etc. may be truncated by an angle delta (Δ) offrom about five (5) degrees to about thirty five (35) degrees before thesegment of curvature defining the corner blend portion, e.g., 122 _(A)becomes tangential to the first face cutting edge portion 154 _(A). Insome embodiments, the segment of curvature used to provide the cornerblend portions 122 _(A), etc. may be truncated by an angle delta (Δ) offrom about ten (10) degrees to about twenty five (25) degrees before thesegment of curvature defining the corner blend portion, e.g., 122 _(A)becomes tangential to the first face cutting edge portion 154 _(A). Byanother measure, in an embodiment, and as also depicted in FIG. 18A, thesegment of curvature used to provide the corner blend portions 122 _(A),etc., may be truncated with about 0.002 inches or more spacing T beforesuch segment of curvature defining the corner blend portion, e.g., 122_(A) becomes tangential to the first face cutting edge portion 154 _(A).In other embodiments, by similar measure, the segment of curvature usedto provide the corner blend portions 122 _(A), etc. may be truncatedwith between about 0.003 inches and about 0.0005 inches of spacing Tbefore such segment of curvature defining the corner blend portion,e.g., 122 _(A) becomes tangential to the first face cutting edge portion154 _(A).

In an embodiment, as can also be appreciated by reference to FIG. 18A,the corner blend portions 122 _(A) etc. may be blended tangential to therespective flute cutting edge 134 _(A), etc. to provide a smooth blendfrom the periphery of the cutter 101 upwardly extending toward therespective first dish portions 152 _(A), etc., by fully utilizing theradius R_(C) to the outer diameter of the tool at the periphery, i.e.,at flute cutting edge 134 _(A) of flute 114 _(A).

In yet another embodiment, as illustrated in FIG. 18B, the corner blendportions 122 _(A) etc. may be provided with an outer surface curvaturedefined by a segment of curvature shaped from a conic element, andwherein the segment of curvature is blended tangential to the first facecutting edge portion 154 _(A). In such case, the spacing T is reduced tozero, as tangency is achieved between the corner blend portions 122 _(A)etc. and the first face cutting edge portions 154 _(A) and the like.

As seen in FIG. 18C, in yet another embodiment, the corner blendportions 122 _(A), etc., may be provided with an outer surface profiledefined by one or more chamfer portions 160 and 162.

Attention is now directed to FIGS. 4, 5 and 6, wherein an embodiment fora rotary cutting tool is shown having at least one coolant channelpassageway 164 defined by in this case by cylindrical interior edgewalls 166. In this embodiment, the cooling channel is located along therotational longitudinal centerline 168 of cutter 100 _(C). The bottom108 _(C) of cutter 100 _(C) provides an entry port 170 for coolantrepresented by reference arrow 172 to enter the shank portion 106 _(C).Coolant is further represented by reference arrow 174 to be movingthrough cutter 100 _(C), and then leaving cutter 100 _(C) via exit port176 as depicted by reference arrow 178, as better seen in FIG. 5.

Alternately, as depicted in FIG. 4A, coolant channels may be providedwith entry port 170 to a common entry channel 164 s on the shank portion106 _(C), but with separate coolant channels in one or more flutes 114_(A) etc., and exit ports 178 _(A), 178 _(D), allowing coolant to bedischarged indirectly from flutes as suitable for a particularapplication, such as at second dish portion 156 _(A), (see FIGS. 4A and4B) or gashes (see FIGS. 18A-18C and 19).

In yet another embodiment, as depicted in FIG. 4B, coolant channels maybe provided with multiple entry ports 170A, 1700, etc. for use withcoolant channel passageways in specific flutes 114 _(C), 114 _(D), etc.,as suitable for a particular application, and with corresponding exitports 178 _(A), 178 _(D), etc, as useful in such circumstance. Variouscoolant channel passageway structures may be provided via suitabletechniques such as electrical discharge machining (“EDM”) processes, orby drilling with diamond bit, as may be suitable in specific toolmaterials. In this manner, at least a portion of one or more coolantchannels in the body of cutter 100 _(C) are located along and within atleast a portion of one or more of the flutes 114 _(A), etc, as noted.

Attention is now directed to FIGS. 7, 9, 10, and 11, which depict adesign for a three flute cutter 200 having flutes 214 _(A), 214 _(B),and 214 _(C), with details similar to those described in detail abovewith respect to flutes 114 _(A), 114 _(B), and 114 _(C) in a five flutedesign. FIG. 8 is a design for a similar cutter 200 _(G), however,smoothly radiused gashes 202 are provided in the flutes 214 _(AG), 214_(BG), and 214 _(CG). Attention is directed to FIGS. 10 and 11, withrespect to the cutting end or face portion 250 of cutter 200 depicted inFIG. 9. A first dish portion 252 _(A), 252 _(B), and 252 _(C),(extending from each flute that runs to the face end 251 of the cutter200 _(G), respectively) slopes downwardly and inwardly (along respectivefirst face cutting edge portions 254 _(A), 254 _(B), and 254 _(C)) at afirst dish angle alpha (α), as described above. Also, as may beappreciated from FIG. 11 in an embodiment, a second dish portion, 256_(A), 256 _(B), and 256 _(C), slopes downwardly and inwardly (along arespective second face cutting edge portions 258 _(A), 258 _(B), and 258_(C)) at a second dish angle beta (β), as generally described above.Also, similar to earlier configurations described above, corner blendportions (222 _(A), 222 _(B), and 222 _(C)) are shown extending fromtheir respective flute cutting edge (234 _(A), and also 234 _(B) and 234_(C) which are similar, but not seen in FIG. 9) and their companionfirst face cutting edge portions (254 _(A), 254 _(B), and 254 _(C)). Thecorner blend portions 222 _(A), etc. may be provided in various preciseshapes as appropriate for a particular service, generally as notedabove.

With respect to FIG. 12, cutter 137 provides a three flute design ashaving v-shaped notches 260 in flutes 264 _(A), 264 _(B), and 264 _(C).

Referring now to FIG. 14, a side view of a cutting end of milling cutter300 is provided. For ease of viewing, only two opposing flutes 314 _(A)and 314 _(B) are shown along with the tip end 310 of milling cutter 300.The tip end 310 includes the gashed end or extension of each flute 314_(A) and 314 _(B). Further, starting at the centerline 318 at the innerend 320 of cutter 300, and moving outward (to the right in FIG. 14), itcan be appreciated that a point of tangency 321 occurs where the cornerblend portion 322 _(A) is tangent to the outer circumference of cutter300 at leading edge land portion 332 _(A) and flute cutting edge 334_(A). Reversing direction, from that circumferential point of tangency321 and moving inwardly along corner blend portion 322 _(A), a point ofintersection 323 occurs where first face cutting edge portion 354 _(A)of the first dished portion 352 _(A) meets, and truncates, the arc ofcorner blend portion 322 _(A). Thus, an arc that provides less than fulltangency between leading edge land portion 332 _(A) and the first facecutting edge portion 354 _(A) of the first dished portion 352 _(A) isprovided. In an embodiment, a radii may be provided with respect tocorner blend portion 322 _(A), and such radii may complete 89 degrees orless of the arc at point of interception 323 with first end dish 352_(A).

The first dished portion 352 _(A) (or 352 _(B)) slopes downwardly andinwardly (along respective first face cutting edge portions 354 _(A) or354 _(B), at a first dish angle alpha (α), as described above. In anembodiment, the angle alpha (α), may be provided at an angle of betweenabout 6 and about 25 degrees. In an embodiment, the angle alpha (α), maybe provided at an angle of between about 6 and about 15 degrees. In yetanother embodiment, angle alpha (α), may be provided at an angle ofbetween about 8 and about 17 degrees. The corner blend portions 222_(A), etc. may be provided in various precise shapes as appropriate fora particular service, generally as noted above.

Also as may be appreciated from FIG. 14, in an embodiment, a second dishportion, 256 _(A) or 256 _(B), slopes downwardly and inwardly (along arespective second face cutting edge portions 258 _(A) or 258 _(B)), at asecond dish angle beta (β), as generally described above. In anembodiment, the second dish angle beta (β) may be between about 15 andabout 75 degrees. In another embodiment, second dish angle beta (β), maybe between about 45 degrees and 118 degrees. Adjacent to the second dishportions 256 _(A) and 256 _(B) is the end face gash 340. Primary endface clearance angle alpha (α), and secondary end face clearance anglebeta (β) provide clearance on the end 310 of the cutting tool 300.

Use of a truncated intersection, such as a radii, at intersection 323 onthe cutting tool 300 is useful and may be advantageous in variousapplications. However, providing a corner blend portion 322 _(A) viaalternate configuration, such as via one or more chamfers, or that forma conic segment or an elliptical, hyperbolic, parabolic, or other shapemay be advantageous in various sizes while allowing additional strengthand providing good chip flow during use of cutting tool 300 withaggressive ramping. The formed corner at 323 as described herein allowsfor better distribution of strain and heat generated at cutting edges,as there is more surface area and mass available for transfer of theresulting heat. The shape and thickness of a chip, and the area of ashear zone during use of the tool, including the flow path of the chipcreated, is thus controlled, also causing a reduction in friction andheat during use. And, strength may be provided to the tool with theaddition of such non-tangential form. And, since such a corner blendconfiguration such as use of a truncated curve or radii, allows the chipfrom the tool to flow freely. Also, this configuration creates atransitional cutting face other than a sharp corner, mass and areabetter able to distribute heat helping to prevent plastic deformation,as compared to other designs of which we are aware. And, the cuttingtool 300 itself is thus stronger, and therefore less subject tochipping.

In various embodiments, cutting tools such as cutting tool 100 or 300may include a body made of high speed steel (as such term is used bythose of skill in the art and to whom this specification is directed;see http://en.wikipedia.org/wiki/High_speed_steel, for example), or bythe functional equivalents thereof. By way of example, currentlyavailable “high speed steels” include steel grades designated as M2 (ageneral purpose medium mechinability high speed tool steel), M3, M7(with molybdenum, tungsten, chromium and vanadium—see the AmericanSociety for Testing Materials ASTM Specification A600, for example), andM42 (includes cobalt alloy). Also, PM materials, i.e. powdered metal orparticulate materials for various tool bits, may be utilized. Anotherexample includes Toolox44 brand machine steel manufactured by SSABOxelosund AB of Oxelosund, Sweden (see http://www.toolox.com). Invarious embodiments, cutting tools such as cutting tool 100 or 300 mayhave flutes or the body made of high strength steel, tungsten carbide,cermet, or ceramic materials. In an embodiment, a rotary cutter as setforth herein may have flutes made from a first flute material, and thebody made from a second material. Also, in an embodiment, the flutecutting edges may be provided in a first edge material, and the body maybe made of steel, including high strength steel. Also, the shank portionmay be fabricated from a first shank material, and the flutes from afirst flute material, and wherein the first shank material and the firstflute material are securely attached with a mechanical jointtherebetween. Such mechanical joint may be a threaded joint. Suchmechanical joint may be a tapered joint. Further, such a mechanicaljoint may be a welded joint, a soldered joint, or a brazed joint. And,to provide a high quality tool, at least the cutting portion of the toolmay have a surface treated using a selected tool performance enhancementprocess, such as (a) physical vapor deposition (PVD), (b) chemical vapordeposition (CVD), (c) flute polishing, (d) cryogenic tempering, (e)sputtering, and (f) diamond impregnation. And, various sputteringprocesses may be utilized, including (a) magnetron sputtering, (b) heatspike sputtering, (c) preferential sputtering, (d) electronicsputtering, and (e) physical sputtering.

As just described, and as also seen in FIGS. 15 and 16, in anembodiment, the rotary cutter or end mill 300 has an increased firstdish angle alpha of from about six (6) to fifteen (15) degrees, and asecond dish angle beta from about fifteen (15) to about seventy five(75) degrees, while maintaining ample strength at the end 310 of therotary cutter or end mill 300. Such angle alpha (α) also reduces toolpressure when using the tool while ramping at an angle that is less thanthe first dish angle alpha (α) on the end of the cutting tool 300. Whenramping at an angle less than the first dish alpha (α) on the end 310 ofthe cutting tool 300, the cutting tool 300 cuts only on the leadingdiameter of the cutting tool 300, and the first and at times the secondface cutting edge portions 258 _(A) or 258 _(B), at a second dish anglebeta (β), as generally described above, i.e. on the backside of innercutting edges 258 _(A) and 258 _(B). This reduces the amount of overallcutter contact with a workpiece, as the most advantageous ramp anglesare greater than five (5) degrees.

Various cutter designs as described herein, such as cutting tool 300, orcutter 100, with the extremely narrow peripheral leading edge landportion 332 _(A) and accompanying first cutting edge portion 354 _(A)have shown considerable improvement over prior art cutter designs,especially when tested at very high surface feet per minute. Whenmachining at high surface footage, as mentioned above, a cutting edgepreparation to provide honing of the flute and face cutting edges in therange of from about five one-hundred thousandths of an inch (0.00005inches) to about three thousandths of an inch (0.003 inches) helps toprevent cutter chatter from to modal coupling, while showing asignificant reduction in tool cutting pressures and heat generation.

Addition of coolant delivery through the body of the end mill hasalready been discussed in connection with FIGS. 4, 4A, and 4B above.Coolant delivery may be provided with a single hole located along thecentral axis of an end mill, through multiple holes parallel to thelongitudinal axis, or with a spiral that matches the helix of the flutesand periphery cutting edges. Cooling exit ports may be provided as theapplication requires. The addition of a coolant hole or holes makes itpossible to deliver coolant to the interior cutting edges at a widerange of spindle operational speeds (i.e., revolutions per minute), andeven at very high spindle (rotary) speeds. The delivery of coolantthrough the body of the cutter to the end of the tool provides coolingto the core of the cutter body in addition to providing lubrication andcoolant to the cutting face, including the first and second dishportions located at the inner tip of a tool. The supplied coolant thenflows outwardly, thus cooling and lubricating the peripheral edges, i.e.the flute cutting edges. Another benefit of delivering coolant throughthe body of the end mill is that of chip evacuation. Chip evacuation atthese high and maintainable feed rates using the rotary cuttersdescribed herein poses a challenge and is one of the largest obstacleswhen performing an aggressive helical ramp or pocket milling. With mostif not all prior art cutters for similar work, coolant is supplied fromthe outside inward, often deflecting chips back in towards the pocketand cutter, causing such often work-hardened chips to be re-cut, orsmashed between the outer periphery of the cutting edge and the workpiece. The improvement described herein, of providing coolant throughthe cutter body, eliminates the problem of coolant pushing chips back intowards the cutter, as coolant flow is from the inside outward, thuscarrying chips away from the cutter. This is a significant improvementin the art, and greatly reduces the incidence of re-cutting chips,especially when aggressive ramp angles are combined with helical entry.The vastly increased ramp capabilities usable when employing rotarycutters as described herein now allows one to make holes, in many cases,faster than if a drill were used to manufacture such hole in aworkpiece.

The rotary cutters as described herein may be advantageously employedfor cutting or rough milling a workpiece 500, for example as noted inFIG. 20, where the workpiece is machined at ramp angle sigma (Σ) using acutter 100 _(C). Cutters fabricated according to the design set forthherein provide improved ramping capability as compared to prior arttools of which we are aware, especially when milling using ramping orhelical plunging into solid material while making a hole or pocket. Forexample, when a workpiece 500 comprises steel, typical prior art rotarycutters operate at a about a two (2) degree ramp angle, at a feed rateof about fifteen (15) inches per minute (IPM), whereas a cutter such ascutter 100 _(C) as described herein would operate at a ramp angle ofbetween about eight (8) and twelve (12) degrees, at a surface feed rateof about sixty (60) inches per minute (IPM). Similarly, when a workpiece500 comprises titanium, typical prior art rotary cutters operate at aabout a one (1) degree ramp angle, at a surface feed rate of about ten(10) inches per minute (IPM), whereas a cutter such as cutter 100 _(C)as described herein would operate at a ramp angle of between about three(3) and five (5) degrees, at a feed rate of about forty (40) inches perminute (IPM). Further, when a workpiece 500 comprises aluminum, typicalprior art rotary cutters operate at a about a ramp angle of between six(6) and ten (10) degrees at a surface feed rate of about thirty (30)inches per minute (IPM), whereas a cutter such as cutter 100 _(C) asdescribed herein would operate at a ramp angle of between about twelve(12) and thirty five (35) degrees, at a surface feed rate of up to asmuch as about one hundred seventy (170) inches per minute (IPM).Generally, surface feed rates and ramp angles when milling using helicalramping with cutters as described and claimed herein are from about four(4) to about six (6) times faster than is achievable using prior artrotary cutter designs. More specifically, in an embodiment, the novelcutter designs set forth and claimed herein enable both much highersurface feed rates and the use of steeper helical ramp angles, thusmaking entry into a solid workpiece much easier than was heretofore thecase.

Further, in various embodiments, it may be advantageous to vary the typeand spacing of flutes in a rotary cutter design. In an embodiment, itmay be advantageous to provide straight flutes, rather than helicalflutes, for example, if the rotary cutter is to be used for cuttingsuitable materials such as cast iron. FIG. 19 provides an overview ofsuch options. Generally, as already illustrated, a rotary cutting toolmay be provided with a plurality of helical flutes. In variousembodiments, such plurality of helical flutes comprises N flutes,wherein N is a positive integer. The positive integer may be between two(2) and seven (7) for many commonly required tool sizes, but the numberof flutes may be more, or less, i.e., only one (1), or eight (8), ormore. In an embodiment, each of the helical flutes may have a commonuniform helical angle. Alternately, only one (1), or more than one (1)of the helical flutes may have the same helical angle along its length.Further, in an embodiment, one (1) or more of the helical flutesprovided may have a helical angle which varies along its length.Further, in yet another embodiment, the multiple helical flutes may havehelical angles which all vary in common along their length. And, in anembodiment, a rotary cutter may be provided within a plurality ofhelical flutes, and wherein each of the helical flutes have a differenthelical angle.

Turning to FIG. 17, in an embodiment, a cutter 400 may be provided whereonly a single dish angle alpha (α) is utilized. In an embodiment, asingle dish angle alpha (α) of more than three (3) degrees may beutilized. Two opposing flutes 414A and 4148 are shown along with the tipend 410 of milling cutter 400. Starting at the centerline 418 at theinner end 420 of cutter 400, and moving outward (to the right in FIG.17), it can be appreciated that a point of tangency 421 occurs where thecorner blend portion 422A is tangent to the outer circumference ofcutter 400 at leading edge land portion 432A and flute cutting edge434A. Reversing direction, from that circumferential point of tangency421 and moving inwardly along corner blend portion 422A, a point ofintersection 423 occurs where first cutting edge portion 454A of thefirst dished portion 452A meets, and truncates, the arc of corner blendportion 422A. Thus, an arc that provides less than full tangency betweenleading edge land portion 432A and the first cutting edge portion 454Aof the first dished portion 452A is provided.

Historically, the software available for control of cutting tools inmachining operations has not addressed the uniformity and precisioncontrol of radial engagement depth, or of tool engagement angle.Consequently, prior art rotary cutter tool designs have historicallybeen provided with a core diameter in the range of from about fifty fivepercent (55%) to about fifty eight percent (58%) of overall tooldiameter. Such designs allowed the tool to utilize deep flutes, whichprovided room to accommodate long chips. Such long chips might have beengenerated, for example, when set up with one hundred twenty (120) degreeor full slotting, or when encountering a one hundred eighty (180) degreetool engagement angle such as might occur when a rotary cutter enters acorner. Such prior art tools were capable of accepting long chips andlarge chips, since such prior art rotary cutters were normally providedwith a deep flute gullet. Wide variation in chip size is encountered intraditional tool path configurations since the tool engagement anglesignificantly increases when cutting into a corner of a workpiece, forexample.

In an embodiment, the rotary cutters described and claimed herein havebeen designed for effective utilization and definition of tool geometryto enhance cutting efficiency when using advantageous rotary cutterpaths through a workpiece such as are described in U.S. Pat. No.7,577,490 B2, issued Aug. 18, 2009 to Diehl et al., entitled ENGAGEMENTMILLING, and in U.S. Pat. No. 7,451,013 B2, issued on Nov. 11, 2008 toColeman et al., entitled ENGAGEMENT MILLING; the disclosures of each ofthose patents are incorporated herein in their entirety by thisreference. Both of those patents are assigned to Surfware, Inc. ofWestlake Village, Calif., who provides engagement milling softwaremarketed under their TRUEMILL® brand, to enable users of CNC machinesand the like in computer aided manufacturing (CAM) systems to improveproductivity. See further details athttp://www.truemill.com/content/truemill-true-engagement-milling, orcontact by mail at 3200 Corte Malpaso, #104, Camarillo, Calif. 93012.Such advantageous cutter paths assist in optimization of rotary cutterefficiency by carefully and precisely controlling the tool engagementangle, thereby providing, in an embodiment, relatively uniform radialengagement depth with respect to the workpiece, as well as relativelyuniform axial depth of cut, and thus providing relatively uniform rotarycutter loading and heat dispersal. Thus, in an embodiment, such rotarycutter designs provide for relatively uniform chip length and chipthickness. In one aspect, such advantageous cutter paths enableestablishment of limits on tool loading, such as radial force on a tool,and thus, tool deflection is limited. In another aspect, suchadvantageous cutter paths enable establishment of limits on force onflutes on the tool, which limits the tangential force on the tool, andthus, assists in providing for long tool life. In another aspect, suchadvantageous cutter paths enable limiting of maximum tool temperature,and in such a manner also assist in providing for long tool life.Temperature control, and maximum temperature limitations are possiblebecause constant rotary speed can be maintained, chip thickness islimited, and the tool engagement angle is limited. In short, the amountof workpiece material that the cutting edge of the rotary cutter sweepsthrough is controlled and limited, and thus, the resultant heat buildupis limited. By such careful control of tool path, the cutting velocity,generally specified in terms of surface feet per minute (SFM), can beincreased when using the novel rotary cutters described herein, due inpart because the rotary cutter spends minimal time in limited cuts atlarge tool engagement angles. Thus, the material removal rates (MRR) canbe increased, since larger axial depth of cuts can be provided whilemaintaining uniform chip size and high cutting velocities.

In an embodiment, the rotary cutters described herein may take advantageof the tool paths enabled by the techniques described by the Diehl etal. and the Coleman et al. patents just noted above, to provide improvedcutting performance. In an embodiment the rotary cutters describedherein may be provided with shallow gullets, yet still avoid failure dueto chip packing, since when using such tool paths, the rotary cutternever exceeds a specified tool engagement angle or a specified radialdepth of cut. As an example, in an embodiment, a one (1) inch diameter,five (5) flute rotary cutter may be provided for use in applicationshaving up to a sixty (60) degree engagement angle, with a core diameterof sixty eight percent (68%) of the overall tool diameter. In anembodiment, a rotary cutter may be provided in accord with the teachingsherein with a core diameter of as large as seventy five percent (75%) ofthe overall tool diameter.

Attention is directed to FIG. 21, in which certain key concepts withrespect to use of a rotary cutter on a workpiece are described, using aplan view, looking axially down on a rotary cutter 500 as it acts on aworkpiece 502. Here, rotary cutter 500 with a tool diameter of R_(TOOL)is shown acting to cut workpiece 502 to produce a chip 504. A radialdepth of cut (“RDC”) is indicated. Chip 504 is made by a tooth(indicated as located at point 506 _(O)) at the start of engagement oftooth with workpiece 502 and at point 506 ₁ at the end of engagement thetooth of rotary cutter 500 with workpiece 502, as the rotary cutter 500rotates against workpiece 502. The location of the center of rotation ofrotary cuter 500 at the start of engagement of tooth with workpiece 502is indicated as C_(O). The location of the center of rotation of rotarycutter 500 at the end of engagement of tooth with workpiece is shown asC₁. The rotary cutter 500 tool engagement angle epsilon (ε) isindicated; this is the angle of rotation which is completed duringengagement of a tooth with workpiece 502. Chip 504 is produced in such acut, and an undeformed chip 504 (shown removed from the working area forpurposes of explanation) has a chip thickness (“CT”) equal to the sin(ε) times the feed length per tooth (“FPT”). During the cutting of aworkpiece 502, an axial depth of cut (“ADC”) may be selected andutilized to effectively use flute cutting edges (e.g., 134 _(A) in FIG.2) along at least some length of the cutting portion 110 of a particularrotary cutter such as cutter 101 of FIG. 2. Thus, in milling cutters orendmills as illustrated in the various figures, the material removalrate (MRR) is proportional to the axial depth of cut (ADC). Whenutilizing tool paths as noted above and the novel rotary cuttersdescribed herein, cuts in a workpiece 502 may be accomplished at 1.5 to2 times the rotary cutter outside diameter OD (OD=2 times R_(TOOL)), ormore, or in some embodiments, at about three times the outside diameteror less, for optimizing material removal rates (MRR) and the life of arotary cutter 500. In this manner, production of uniform, but larger andfewer chips 504 result in increasing machining efficiency, as shown bylower power requirements, and less heat produced for a given materialremoval rate. The novel rotary cutter designs provided herein allowcutting of a chip having a chip thickness (CT) produced near, or at, thedesign end point for feed rate per tooth (FPT), especially when usingoptimized tool paths as may be employed when using the TRUEMILL brandcomputerized cutting parameters and machining software.

In order to optimize strength of a rotary cutter or endmill as providedherein, to enable such large material removal rates, as shown in FIG.22, in an embodiment, an endmill is provided having two flutes, whereinthe core diameter CD is at least sixty percent (60%) of the outside tooldiameter OD. As illustrated, two (2) times the tool radius (R_(TOOL))equals the outside diameter OD of the three flute tool 251, and two (2)times the tool core radius (R_(CORE)) equals the core diameter CD of thetwo flute endmill 300. The depth of flute is indicated as DF. The centerof rotation of the various rotary cutters in this and the followingfigures is noted as C.

In order to optimize strength of a rotary cutter or endmill as providedherein, to enable such large material removal rates, as shown in FIG.23, in an embodiment, an endmill 530 is provided having three flutes,wherein the core diameter CD is at least sixty percent (60%) of theoutside tool diameter OD. As illustrated, two (2) times the tool radius(R_(TOOL)) equals the outside diameter OD of the three flute endmill530, and two (2) times the tool core radius (R_(CORE)) equals the corediameter CD of the three flute endmill 530.

In order to optimize strength of a rotary cutter or endmill as providedherein, to enable such large material removal rates, as shown in FIG.24, in an embodiment, an endmill 540 is provided having four flutes,wherein the core diameter CD is at least fifty eight percent (58%) ofthe outside tool diameter OD. As illustrated, two (2) times the toolradius (R_(TOOL)) equals the outside diameter OD of the four fluteendmill 540, and two (2) times the tool core radius (R_(CORE)) equalsthe core diameter CD of the four flute endmill 540. As illustrated, thefour flute endmill 540 has a core diameter CD of at least sixty percent(60%) of the outside diameter OD of four flute endmill 540.

In order to optimize strength of a rotary cutter or endmill as providedherein, to enable such large material removal rates, as shown in FIG.25, in an embodiment, an endmill 550 is provided having five flutes, andwherein the core diameter CD is at least sixty one percent (61%) of theoutside tool diameter OD. As illustrated, two (2) times the tool radius(R_(TOOL)) equals the outside diameter OD of the five flute endmill 550,and two (2) times the tool core radius (R_(CORE)) equals the corediameter CD of the five flute endmill 550. As illustrated, the fiveflute endmill 550 has a core diameter CD of at least sixty four percent(64%) of the outside diameter OD of five flute endmill 550.

In order to optimize strength of a rotary cutter or endmill as providedherein, to enable such large material removal rates, as shown in FIG.26, in an embodiment, an endmill 560 is provided having six flutes, andwherein the core diameter CD is at least sixty three percent (63%) ofthe outside tool diameter OD. More preferably, the core diameter of sixflute endmill 560 is at least sixty five percent (65%) of the outsidetool diameter OD. Even more preferably, the core diameter of six fluteendmill 560 is at least sixty five percent (65%) of the outside tooldiameter OD. As illustrated, two (2) times the tool radius (R_(TOOL))equals the outside diameter OD of the six flute endmill 560, and two (2)times the tool core radius (R_(CORE)) equals the core diameter CD of thesix flute endmill 560.

In order to optimize strength of a rotary cutter or endmill as providedherein, to enable such large material removal rates, as shown in FIG.27, in an embodiment, an endmill 570 is provided having seven flutes,and wherein the core diameter CD is at least sixty-four percent (64%) ofthe outside tool diameter OD. More preferably, the core diameter ofseven flute endmill 570 is at least sixty eight percent (68%) of theoutside tool diameter OD. As illustrated, two (2) times the tool radius(R_(TOOL)) equals the outside diameter OD of the seven flute endmill570, and two (2) times the tool core radius (R_(CORE)) equals the corediameter CD of the seven flute endmill 570.

In order to optimize strength of a rotary cutter or endmill as providedherein, to enable such large material removal rates, as shown in FIG.28, in an embodiment, an endmill 572 is provided having seven flutes,and wherein the core diameter CD is at least sixty seven percent (67%)of the outside tool diameter. More preferably, the core diameter ofseven flute endmill 572 is at least sixty eight percent (68%) of theoutside tool diameter OD. As illustrated, two (2) times the tool radius(R_(TOOL)) equals the outside diameter OD of the seven flute endmill572, and two (2) times the tool core radius (R_(CORE)) equals the corediameter CD of the seven flute endmill 572. As illustrated in FIG. 28,the seven flute endmill 572 has a core diameter CD of sixty eight pointone four percent (68.14%) of the outside diameter OD of seven fluteendmill 572.

Various embodiments for an endmill as just set forth above may beutilized in a method of removing material from a workpiece using arotary cutter. In such a method a rotary cutter is provided. The rotarycutter or endmill will have a selected outside diameter and a selectedcore diameter, and the selected core diameter will be greater than sixtypercent of the selected outside diameter. The workpiece may be milledusing a selected ramp angle broadly in the range of from about fivedegrees to about thirty five degrees. The rotary cutter may be used withan axial depth of cut of from about one point five to about three timesthe outside diameter of the rotary cutter. The number of flutes andcorresponding core diameters may be selected for a particular cutter asjust set forth above.

By providing large core diameters, as just described, the strength ofthe rotary cutter is greatly increased, thus allowing far larger loadsthan could be supported by prior art milling rotary cutters of which weare aware. Such increased loading is created by increased axial depth ofcut and by increased chip thickness. Also, providing a larger corediameter as taught herein increases the rigidity of a rotary cutter,thus reducing the effect of modal coupling, and as a consequence,significant increases in cutter speed and feed rate are possible,without chatter. Note that the core diameters as set forth in thepreceding paragraphs are applicable to the novel rotary cuttersdisclosed herein in various embodiments wherein the rotary cutters havean outside tool diameter and a core diameter and wherein such rotarycutters have a usable cutting portion A_(L) (see FIG. 2) having a lengthof less than or equal to about three times said outside tool diameterOD, to thereby enable an axial depth of cut (ADC) on a workpiece as deepas the length A_(L) of the usable cutting portion of the rotary cutter.

When prior art endmills with conventional flute depth and/or corediameter are run at the rotary speeds and workpiece feed rates as arepossible to routinely achieve using the novel rotary cutter describedherein, the result is often the catastrophic failure of such prior arttools, since such prior art tools do not have sufficient strength, incross-section, due to smaller core diameters, in order to withstandstress from greatly increased cutting forces.

In the foregoing description, for purposes of explanation, numerousdetails have been set forth in order to provide a thorough understandingof the disclosed exemplary embodiments for the design of a novel rotarycutting tool. However, certain of the described details may not berequired in order to provide useful embodiments, or to practice aselected or other disclosed embodiments. Further, for descriptivepurposes, various relative terms may be used. Terms that are relativeonly to a point of reference are not meant to be interpreted as absolutelimitations, but are instead included in the foregoing description tofacilitate understanding of the various aspects of the disclosedembodiments. And, various actions or activities in a method describedherein may have been described as multiple discrete activities, in turn,in a manner that is most helpful in understanding the present invention.However, the order of description should not be construed as to implythat such activities are necessarily order dependent. In particular,certain operations may not necessarily need to be performed in the orderof presentation. And, in different embodiments of the invention, one ormore design or assembly activities may be performed simultaneously, oreliminated in part or in whole while other design or assembly activitiesmay be added. Also, the reader will note that the phrase “in anembodiment” or “in one embodiment” has been used repeatedly. This phrasegenerally does not refer to the same embodiment; however, it may.Finally, the terms “comprising”, “having” and “including” should beconsidered synonymous, unless the context dictates otherwise.

Further, it should be understood by those of skill in the art and towhom this specification is directed that the term “conic” refers to theintersection of a plane and a conical surface, which may result in anelliptical shape, a parabolic shape, or a hyperbolic shape. Further, inthe case where the axes of the elliptical shape are equal, a circleresults, and thus a constant radius curve would be described.

Importantly, the aspects and embodiments described and claimed hereinmay be modified from those shown without materially departing from thenovel teachings and advantages provided by this invention, and may beembodied in other specific forms without departing from the spirit oressential characteristics thereof. Therefore, the embodiments presentedherein are to be considered in all respects as illustrative and notrestrictive or limiting. As such, this disclosure is intended to coverthe structures described herein and not only structural equivalentsthereof, but also equivalent structures. Numerous modifications andvariations are possible in light of the above teachings. Therefore, theprotection afforded to this invention should be limited only by theclaims set forth herein, and the legal equivalents thereof.

1. An endmill, the endmill having an outside tool diameter, a corediameter, and an end face portion, wherein the endmill comprises flutecutting edge portions and face cutting edge portions, and wherein theendmill further comprises corner blend portions extending from flutecutting edge portions to face cutting edge portions, wherein the facecutting edge portions slope inwardly and downwardly at a first dishangle alpha (α) in a range of from about five point five (5.5) degreesto about twenty five (25) degrees, and wherein the endmill furthercomprises one or more coolant passageways therethrough, and wherein atleast one of the one or more coolant passageways exits at an exit portlocated on the end face portion, and wherein the exit port is located ata center of rotation of the end face portion.
 2. An endmill as set forthin claim 1, wherein the endmill comprises one or more gash portions, andwherein at least one of the one or more coolant passageways therethroughcomprises an exit port located on a gash portion.
 3. An endmill as setforth in claim 1, wherein the endmill comprises one or more dishportions, and wherein at least one of the one or more coolantpassageways therethrough comprises an exit port located on a dishportion.
 4. An endmill as set forth in claim 3, wherein the dish portioncomprises a first dish portion.
 5. An endmill as set forth in claim 4,wherein the dish portion comprises a second dish portion.
 6. An endmillas set forth in claim 1, wherein the exit port is located at a center ofrotation of the end face portion.
 7. An endmill as set forth in claim 1or 6, wherein the endmill comprises flute cutting edge portions and facecutting edge portions, and wherein the endmill further comprises cornerblend portions extending from flute cutting edge portions to facecutting edge portions.
 8. An endmill as set forth in claim 7, whereinthe face cutting edge portions slope inwardly and downwardly at a firstdish angle alpha (α) in a range of from about five point five (5.5)degrees to about twenty five (25) degrees.
 9. An endmill as set forth inclaim 1, wherein the endmill has two or more flutes, and wherein thecore diameter is at least sixty percent (60%) of the outside tooldiameter.
 10. An endmill as set forth in claim 9, wherein the endmillhas three flutes.
 11. An endmill as set forth in claim 9, wherein theendmill has four flutes.
 12. An endmill as set forth in claim 1, whereinthe endmill has five flutes, and wherein the core diameter is at leastsixty one percent (61%) of the outside tool diameter.
 13. An endmill asset forth in claim 12, wherein the core diameter is at least sixty fourpercent (64%) of the outside tool diameter.
 14. An endmill as set forthin claim 1, wherein the endmill has six flutes, and wherein the corediameter is at least sixty three percent (63%) of the outside tooldiameter.
 15. An endmill as set forth in claim 14, wherein the corediameter is at least sixty five percent (65%) of the outside tooldiameter.
 16. An endmill as set forth in claim 1, wherein the endmillhas seven flutes, and wherein the core diameter is at least sixty fourpercent (64%) of the outside tool diameter.
 17. An endmill as set forthin claim 6, wherein the core diameter is at least sixty eight (68%) ofthe outside tool diameter.
 18. An endmill as set forth in claim 9,wherein the endmill has a usable cutting portion with a length of lessthan or equal to three times the outside tool diameter, to therebyenable an axial depth of cut on a workpiece as deep as the length of theusable cutting portion.
 19. An endmill as set forth in claim 1, whereinthe endmill comprises one or more end face clearance portions, andwherein at least one of the one or more coolant passageways therethroughcomprises an exit port located on an end face clearance portion.
 20. Anendmill as set forth in claim 19, wherein the end face clearance portioncomprises a primary end face clearance portion.
 21. An endmill as setforth in claim 19, wherein the end face clearance portion comprises asecondary end face clearance portion.
 22. An endmill, the endmill havingan outside tool diameter, a core diameter, and an end face portion,wherein the endmill comprises flute cutting edge portions and facecutting edge portions, and wherein the endmill further comprises cornerblend portions extending from flute cutting edge portions to facecutting edge portions, wherein the face cutting edge portions slopeinwardly and downwardly at a first dish angle alpha (α) in a range offrom about five point five (5.5) degrees to about twenty five (25)degrees, and wherein the endmill further comprises a single axiallyoriented coolant passageway therethrough, and wherein the coolantpassageway exits at an exit port located at the center of rotation ofthe end face portion.
 23. An endmill, the endmill having an outside tooldiameter, a core diameter, and an end face portion, wherein the endmillcomprises flute cutting edge portions and face cutting edge portions,and wherein the endmill further comprises corner blend portionsextending from flute cutting edge portions to face cutting edgeportions, wherein the face cutting edge portions slope inwardly anddownwardly at a first dish angle alpha (α) in a range of from about fivepoint five (5.5) degrees to about twenty five (25) degrees, and whereinthe endmill further comprises a single axially oriented coolantpassageway therethrough, and wherein the coolant passageway exits at anexit port located at the center of rotation of the end face portion, sothat a cooling medium passing through the coolant passageway exits onlyin an axial direction.
 24. An endmill, the endmill having an outsidetool diameter, a core diameter, and an end face portion, wherein theendmill comprises flute cutting edge portions and face cutting edgeportions, and wherein the endmill further comprises corner blendportions extending from flute cutting edge portions to face cutting edgeportions, and wherein the endmill further comprises a single axiallyoriented coolant passageway therethrough, and wherein the coolantpassageway exits at an exit port located at the center of rotation ofthe end face portion.
 25. An endmill, the endmill having an outside tooldiameter, a core diameter, and an end face portion, wherein the endmillcomprises flute cutting edge portions and face cutting edge portions,and wherein the endmill further comprises corner blend portionsextending from flute cutting edge portions to face cutting edgeportions, and wherein the endmill further comprises a single axiallyoriented coolant passageway therethrough, and wherein the coolantpassageway exits at an exit port located at the center of rotation ofthe end face portion, so that a cooling medium passing through thecoolant passageway exits only in an axial direction.
 26. The end mill asset forth in claim 22 through 25, wherein the end face portion isfurther characterized by the lack of lateral cooling medium passageways.